This invention relates to catheter assemblies for intravascular, i.e., I.V., use.
Several different types of I.V. catheter assemblies are commercially available. Typically, such catheter assemblies provide a hollow flexible cannula extending from the assembly and coaxial with a first passageway within the assembly. Fluid, to be introduced into the blood vessel, is passed through the first passageway and through the cannula. It is customary to insert the distal end of the cannula into the blood vessel with an introducer needle which initially resides within the cannula and which is withdrawn as the latter is properly seated in the blood vessel. Accordingly, when the cannula is to be inserted, the assembly is provided with the introducer needle in place, i.e., with the needle passing through the first passageway, through the cannula and having the piercing end of the needle protruding from the distal end of the cannula. The blood vessel is pierced and the cannula is inserted into the vessel. The needle must now be withdrawn and the assembly must be placed into flow communication with the fluid to be administered.
These multiple operations have proven to be awkward to perform using conventional catheter assemblies and have frequently resulted in difficulties for both the user and the patient. Often, in the course of these manipulations, the cannula dislodges from the blood vessel and must be reintroduced. The steps of removing the needle and introducing administered fluid into flow communication with the cannula have resulted in spillage of both the administered fluid and the patient's blood.
An attempt to simplify the process is represented by a series of suggestions in which the catheter assembly is provided with a second passageway, ultimately in flow communication with the cannula and, at least in part, independent of the first passageway through which the needle resides during catheter introduction. Representative of such suggestions are those disclosed in U.S. Pat. Nos. 4,496,368; 4,020,835; 4,224,943; 4,326,519; 4,314,555; 4,073,297; 4,079,738; 4,311,137; European Patent Applications Nos. 78300235.5 (publication No. 0.000831); 81300238.3 (publication No. 0.034879) and U.K. Pat. Nos. 1,476,643; 2,088,215 and 1,284,537. Typically, these suggestions comprises a branch or arm having the second passageway therethrough and extending from the catheter assembly at an angle with the axis of the first passageway. The distal end of this branch is in flow communication with the distal portion of the first passageway and hence in communication with the cannula. The proximal end of the branch is generally capped or sealed with a piercable elastomeric self-sealing plug. In operation, the catheter assemblies of this type, with the introducer needle in place, may be first primed with the fluid to be administered, i.e., the second passageway is placed in flow communication with a source of the fluid and filled with the same. The cannula is next introduced into the blood vessel and the introducer needle withdrawn thereby allowing fluid to flow through the second passageway and through the cannula. To prevent fluid from flowing proximally through the first passageway the proximal end of the first passageway is typically provided with a so-called self-sealing elastomeric plug through which the introducer needle may pass for introduction and removal.
While the above described system represents an improvement over the prior awkward systems first described, several drawbacks have been encountered. Firstly, while the prevention of unintended flow and contamination is dependent upon the ability of the self-sealing plug to seal upon removal of the needle, the smooth operation of the insertion of the needle and its removal requires the needle to be easily reciprocated axially through the seal. These contrary requirements, calling for both a loose and a tight fit about the needle at the seal point, must be resolved in favor of a tight fit for patient safety reasons and hence have made manipulation of the needle difficult.
In an effort to resolve this problem, rather complex designs have been suggested for providing a relatively loosely fitting resilient seal about the needle during venipuncture and then means for applying force to the seal after the needle has been removed to close the seal. Such designs are illustrated in the aforementioned U.S. Pat. Nos. 4,311,137 and 4,496,348. Needless to say, the complexity of these designs have greatly added to the cost and difficulty of manufacturing such catheter assemblies and have also added to the number of manipulations required in using the assemblies.
Accordingly, there is a need for a simple, inexpensively manufactured catheter assembly which may be more efficiently utilized for I.V. infusion.